This invention relates to an apparatus for soaking steel, in which cold steel pieces stored outside the arrangement are subjected to preheating treatment and subsequently to soaking treatment with or without hot steel pieces delivered from an ingot-making position.
Hitherto, the steel making furnace such as a converter, an open-hearth furnace, an electric furnace or the like has been operated in a batch-wise manner, so that different sorts of steel pieces have been discontinuously produced in the cogging factory. On the contrary, since the rolling mill is operated continuously, the soaked steel pieces must be always supplied continuously to the rolling mill. Thus, some of the excess steel pieces must be temporarily stored outside the arrangement, and an appropriate control of cooling and reheating of such the excess steel pieces is rather difficult, which considerably affects to quality and yield of the products in the subsequent rolling mill as well as the manufacturing capacity in the continuous operation. Furthermore, the so-called walking-beam furnace is known as a furnace useful for soaking treatment, which is designed to reheat the cold steel pieces passed through the cooling treatment. The furnace of this type has the disadvantages in that it heating capacity must be large, and in that the furnace inevitably includes movable components at high operational costs and thus is not tolerable with a labor-saving purpose.
In order to overcome these drawbacks the inventor proposed a method for soaking cold and hot steel pieces in U.S. Pat. No. 4,311,454 issued on Jan. 19, 1982. The soaking furnace and the heating furnace of these apparatus are designed to be high in their inner height so as to enhance an effect in radiative transfer to the steel pieces. Since the steel pieces are subjected to soaking treatment at a high temperature due to the radiative transfer in the soaking furnace, the temperature of waste heat exhausted from the soaking or heating furnace is rather high and heat of the waste gas cannot be sufficiently recovered in the preheating furnace, thus leading to a considerable loss of expensive thermal energy.